Excel 2007 : Excel slider to increase/decrease all values in group

Hello,

I have a group of values (example below) in a model. I would like to use a slider to increase and decrease the values. I would like the middle of the slider to be set at 0 and then be able to move the slider to the right increase by 1 up to say 10 and be able to move the slider to the left to decrease by 1 up to 10. Moving the slider would have the same increase/decrease on each of the values below. One problem I am seeing is that excel prohibits me from entering a negative number in the "format control". Are there any workarounds? If not, how can I do this for only increases? Thanks in advance for your help.
A
1 9
2 8
3 12
4 7
5 15
6 9
7 17
8 21
9 5
10 8